Recently, vehicle manufacturers have been focused on research and development of reducing the weight of vehicles by downsizing the engines and to increase fuel efficiency by increasing the power of engines. With an increase in efficiency of engines, the exhaust systems including exhaust manifold, exhaust pipe, catalyst and the like are exposed to substantially elevated temperatures than those in past. Accordingly, there is a need for increasing the performance of heat protectors, for example, heat shield and heat insulator.
FIG. 1 shows an exemplary view of an exhaust manifold with a conventional heat protector in the art. Referring to FIG. 1, a heat protector 1 is fastened to the top of an exhaust manifold via three brackets 5 and dissipates the heat emitted from an exhaust gas discharged through the exhaust manifold 3. For the heat protector 1, an aluminum-coated steel plate has typically been typically, but aluminum thin plates that are advantageous in weight reduction and function of vehicles have been recently used. Aluminum thin plates have the advantages of high thermal conductivity and excellent heat dissipation. However, aluminum thin plates may be disadvantageous due to complicated shapes of manifolds as a heat protector. As consequence, durability such as tearing and cracks may be formed and noise due to vibration of engines may occur.
Accordingly, in some efforts, heat protectors having improved durability and complemented heat dissipation ability with air has been recently introduced and the heat protectors are manufactured by overlapping two or more sheets of aluminum thin plates and adding various shapes, such as embossing, prominences and depressions, waveforms and the like. However, when two aluminum thin plates are pressed to form a heat protector, technical difficulties may occur in forming such as separation of plates and vibration and noise may still remain after they are formed in a heat protector. Further, the heat-blocking ability may be reduced at an activation temperature or less of a catalyst where thermal efficiency is required to increase in the early stage of traveling. In other words, maximizing the efficiency of an engine may be obtained only by blocking heat at a predetermined level up to the activation temperature of a catalyst in the early stage of driving of a vehicle, but the time to reach the activation temperature of a catalyst may increase, when only the conductivity and heat dissipation of aluminum are considered. Further, for the aluminum thin plates of the related art, two sheets of thin flat plates are overlapped and formed in one waveform pattern, such that an air layer is formed. However, only heat-blocking and heat-dissipating characteristics with simple waveform patterns may be obtained, and the heat-blocking characteristic in the early stage of operation of an engine and the heat-dissipation characteristic cannot be simultaneously obtained. Further, due to insufficient air layer, soundproofing effect for blocking noise caused by vibration may be limited.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.